Electronic assemblies with high capacity curved and bent fin heat sinks and associated methods

ABSTRACT

An electronic assembly comprising one or more high performance integrated circuits includes at least one high capacity heat sink. The heat sink, which comprises a number of fins projecting substantially radially from a core, is structured to capture air from a fan and to direct the air to optimize heat transfer from the heat sink. The heat sink fins can be formed in different shapes. In one embodiment, the fins are curved. In another embodiment, the fins are bent. In yet another embodiment, the fins are curved and bent. Methods of fabricating heat sinks and electronic assemblies, as well as application of the heat sink to an electronic assembly and to an electronic system, are also described.

DIVISIONAL APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 10/716,764, filed on Nov. 19, 2003 now U.S. Pat. No. 7,120,020,which is a divisional of U.S. patent application Ser. No. 09/950,100,filed on Sep. 10, 2001, now U.S. Pat. No. 6,671,172, which are bothincorporated herein by reference.

RELATED APPLICATIONS

The present application is related to the following applications thatare assigned to the same assignee as the present application:

Ser. No. 09/716,510, now U.S. Pat. No. 6,633,484, entitled “HeatDissipating Devices, Systems, and Methods with Small Footprint”;

Ser. No. 09/766,757, now U.S. Pat. No. 6,535,385, entitled“High-Performance Heat Sink Configurations For Use In High DensityPackaging Applications”;

Ser. No. 09/800,120, entitled “Radial Folded Fin Heat Sink”;

Ser. No. 09/860,978, now U.S. Pat. No. 6,479,895, entitled “HighPerformance Air Cooled Heat Sinks Used In High Density PackagingApplications”;

Ser. No. 10/047,101, entitled “Heat Sinks and Methods of Formation”

Ser. No. 09/950,898, now U.S. Pat. No. 6,705,144, entitled “AManufacturing Process for a Radial Fin Heat Sink”;

Ser. No. 09/950,101, now U.S. Pat. No. 6,657,862, entitled “RadialFolded Fin Heat Sinks and Methods of Making and Using Same”; and

Ser. No. 10/656,968, entitled “Electronic Assemblies with High CapacityHeat Sinks and Methods of Manufacture.”

TECHNICAL FIELD

The inventive subject matter relates generally to electronics packagingand, more particularly, to several embodiments of an electronic assemblythat includes a high-performance electronic component and a highcapacity heat sink, and to manufacturing methods related thereto.

BACKGROUND INFORMATION

Electronic components, such as integrated circuits (ICs), are typicallyassembled into packages by physically and electrically coupling them toa substrate, such as a printed circuit board (PCB), to form an“electronic assembly”. The “electronic assembly” can be part of an“electronic system”. An “electronic system” is broadly defined herein asany product comprising an “electronic assembly”. Examples of electronicsystems include computers (e.g., desktop, laptop, hand-held, server,Internet appliance, etc.), wireless communications devices (e.g.,cellular phones, cordless phones, pagers, etc.), computer-relatedperipherals (e.g., printers, scanners, monitors, etc.), entertainmentdevices (e.g., televisions, radios, stereos, tape and compact discplayers, video cassette recorders, MP3 (Motion Picture Experts Group,Audio Layer 3) players, etc.), and the like.

In the field of electronic systems there is an incessant competitivepressure among manufacturers to drive the performance of their equipmentup while driving down production costs. This is particularly trueregarding the packaging of ICs on substrates, where each new generationof packaging must provide increased performance, particularly in termsof an increased number of components and higher clock frequencies, whilegenerally being smaller or more compact in size.

As the internal circuitry of ICs, such as processors, operates at higherand higher clock frequencies, and as ICs operate at higher and higherpower levels, the amount of heat generated by such ICs can increasetheir operating temperature to unacceptable levels, degrading theirperformance or even causing catastrophic failure. Thus it becomesincreasingly important to adequately dissipate heat from ICenvironrments, including IC packages.

For this reason, electronic equipment often contains heat dissipationequipment to cool high-performance ICs. One known type of heatdissipation equipment includes an impinging fan mounted atop a heatsink. The heat sink comprises a plurality of radial fins or rods formedof a heat-conductive material such as copper or aluminum formed around acore. The bottom surface of the core is in thermal contact with the ICto conduct heat from the IC to ambient air. The fan moves air over thefins or rods to enhance the cooling capacity of the heat dissipationequipment. However, with high-performance ICs consuming ever greateramounts of power and accordingly producing greater amounts of heat, heatdissipation equipment must have higher heat dissipation capability thanthat heretofore obtained.

In order to offer higher capacity heat transfer, new heat dissipationequipment must be more efficient. It is difficult for air-cooled heatsinks to grow in size, because equipment manufacturers are undertremendous competitive pressure to maintain or diminish the size oftheir equipment packages, all the while filling them with more and morecomponents. Thus, competitive heat dissipation equipment must berelatively compact in size and must perform at levels sufficient toprevent high-performance components from exceeding their operationalheat specifications.

For the reasons stated above, and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a significant need inthe art for apparatus and methods for packaging high-performanceelectronic components in an electronic assembly that minimize heatdissipation problems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art electronic assemblyincluding a heat sink attached to an IC package;

FIG. 2 is a top view of a prior art radial fin heat sink;

FIG. 3 is a top view of the portion within dashed rectangle 22 of FIG.2, showing an air flow pattern within fins of a prior art radial finheat sink;

FIG. 4 is a side view of a section, taken between dashed line segments24 and 25 of FIG. 2, of a prior art radial fin heat sink positioned uponan IC package;

FIG. 5 illustrates a perspective view of a curved fin heat sink, inaccordance with an embodiment of the inventive subject matter;

FIG. 6 illustrates a top view of the curved fin heat sink shown in FIG.5;

FIG. 7 illustrates a perspective view of an electronic assemblyincluding a curved fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

FIG. 8 illustrates a perspective view of a portion of an electronicassembly including an axial flow fan atop a curved fin heat sink, inaccordance with an embodiment of the inventive subject matter;

FIG. 9 illustrates a top view of the portion within dashed rectangle 56of FIG. 6, showing an air flow pattern within fins of a curved fin heatsink, in accordance with an embodiment of the inventive subject matter;

FIG. 10 illustrates a side view of a section of the curved fin heat sinkshown in FIG. 6, taken between dashed line segments 51 and 53;

FIG. 11 illustrates a perspective view of a bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

FIG. 12 illustrates a top view of a bent fin heat sink, in accordancewith an embodiment of the inventive subject matter;

FIG. 13 illustrates a perspective view of an electronic assemblyincluding a bent fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

FIG. 14 illustrates a schematic view of a fan, including its tangentialand axial air flow components, and a side view of a bent fin heat sinkas positioned upon a sectioned IC package on a substrate, in accordancewith an embodiment of the inventive subject matter;

FIG. 15 illustrates a perspective view of a curved-bent fin heat sink,in accordance with an embodiment of the inventive subject matter;

FIG. 16 illustrates a top view of a curved-bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

FIG. 17 illustrates a perspective view of an electronic assemblyincluding a curved-bent fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

FIG. 18 illustrates an air flow pattern for a prior art radial fin heatsink;

FIG. 19 illustrates an air flow pattern for a bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

FIG. 20 illustrates an air flow pattern for a curved-bent fin heat sink,in accordance with an embodiment of the inventive subject matter;

FIG. 21 illustrates a flow diagram of a method of fabricating a heatsink, in accordance with an embodiment of the inventive subject matter;

FIG. 22 illustrates a flow diagram of a method of fabricating anelectronic assembly, in accordance with an embodiment of the inventivesubject matter; and

FIG. 23 is a block diagram of an electronic system incorporating atleast one electronic assembly with at least one high capacity heat sink,in accordance with an embodiment of the inventive subject matter.

DETAILED DESCRIPTION

In the following detailed description of some exemplary embodiments ofthe inventive subject matter, reference is made to the accompanyingdrawings which form a part hereof, and in which is shown by way ofillustration, but not of limitation, some specific embodiments in whichthe inventive subject matter may be practiced, including a preferredembodiment. These embodiments are described in sufficient detail toenable those skilled in the art to understand and practice them, and itis to be understood that other embodiments may be utilized and thatstructural, mechanical, compositional, and procedural changes may bemade without departing from the spirit and scope of the inventivesubject matter. The following detailed description is, therefore, not tobe taken in a limiting sense, and the scope of embodiments of theinventive subject matter is defined only by the appended claims. Suchembodiments of the inventive subject matter may be referred to,individually and/or collectively, herein by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed.

The inventive subject matter provides a solution to thermal dissipationproblems that are associated with prior art packaging of integratedcircuits that have high circuit density and that operate at high clockspeeds and high power levels, by employing a high capacity heat sink.Various embodiments are illustrated and described herein.

In one embodiment, the heat sink comprises a thermally conductive core.The core has a number of thermally conductive fins projecting from it ina substantially radial fashion. The core can have a central cavity intowhich a thermally conductive material is inserted. The heat sink finscan be formed in various shapes. In one embodiment, the fins are curved.In another embodiment, the fins are bent. In yet another embodiment, thefins are curved and bent.

In one embodiment, the heat sink can be used in an electronic assemblyhaving an impinging fan, e.g. an axial flow fan, directing air onto anupper face of the heat sink. The lower face of the heat sink is inthermal contact with a heat-generating electronic component such as ahigh performance IC. The heat sink is structured to capture air from thefan and to direct the air to optimize heat transfer from the heat sink.

Various methods of fabricating heat sinks and electronic assemblies arealso described.

FIG. 1 is a perspective view of a prior art electronic assembly 1including a heat sink 2 attached to an IC package 5. Electronic assembly1 comprises a plurality of electronic components 5-9 mounted upon aprinted circuit board (PCB) 3. Heat sink 2 comprises a relatively thick,flat base plate 12 and an array of fins 11 extending to the edge of andsubstantially perpendicular to the base plate 12. Although the fins 11shown in FIG. 1 are folded fins, other prior art heat sinks do not havefolded fins. For example, it is known in the prior art to use brazed,machined, or extruded solid fins. Base plate 12 is clamped to IC package5 through an attachment device 13. Base plate 12 is often formed ofsolid copper, and it contributes a significant amount of cost and massto electronic assembly 1.

While the sizes of packaged, high performance ICs are decreasing, theamount of heat generated by these components per unit volume isincreasing. Increasing the heat dissipation capabilities of the priorart heat sink 2 would require enlarging the surface area of the baseplate 12 and/or the array of fins 11. This in turn would result inconsuming more PCB real estate, which is generally not a viable optionin an environment where system packaging densities are increasing witheach successive, higher performance, product generation.

Prior art heat sink 2 illustrated in FIG. 1 can be used in conjunctionwith an axial flow fan (not shown in FIG. 1) to increase heatdissipation from the array of fins 11. An axial flow fan has a spinningimpeller that is generally shaped like an airfoil. One component of theair flow emanating from an axial flow fan moves parallel to the axisabout which the impeller rotates, and this “axial component” is directednormal to the array of fins 11 of the heat sink 2, i.e. perpendicular tothe PCB 1. (Refer to axial component 132 in FIG. 14.)

Another component of the air flow from an axial flow fan is tangentialto the impeller's direction of rotation. This “tangential component”results in air swirling about the impeller's axis of rotation. (Refer totangential component 130 in FIG. 14.) The ratio of air being moved bythe axial component versus the tangential component varies with theparticular fan blade geometry. For example, low angles of attack in thefan blade generally result in a higher ratio of axial flow, while highangles of attack generally result in a higher ratio of tangential flow.In some axial flow fans, the ratio is 1:1.

When an axial flow fan is mounted facing downward on prior art heat sink2, its axial component of air flow provides substantially all of thecooling effect, because very little of the tangential component of airflow is captured by the straight vertical fins 11.

FIG. 2 is a top view of a prior art radial fin heat sink 20. Heat sink20 is referred to as a “radial fin heat sink”, because its fins 21emanate radially from a central core 41. Fins 21 are substantiallystraight, and the base of each fin 21 is attached to core 41 parallel toa central axis 42 (refer to FIG. 4). Referring back to FIG. 2, core 41can have a central cavity 23, and a thermal plug 40 of thermallyconductive material can reside within cavity 23 to enhance thermaldissipation.

FIG. 3 is a top view of the portion within dashed rectangle 22 of FIG.2, showing an air flow pattern within fins of the prior art radial finheat sink 20 shown in FIG. 2. In FIG. 3, a tangential air flow component29 from an axial flow fan (not shown) impinges upon fins 26 and 27.

Before discussing tangential air flow component 29, it should be firstnoted that fins 26 and 27 are substantially perpendicular to core 41,and that fins 26 and 27 diverge considerably as they emanate from core41. The radius 43 at the base of fins 26 and 27 is substantially smallerthan the fin tip distance 28 at the tips of fins 26 and 27.

Tangential air flow component 29 impinges against the fins of prior artradial fin heat sink 20, such as fins 26 and 27. A major portion 30 oftangential air flow component 29 moves outwardly towards the tips offins 26 and 27. A smaller portion 33 of tangential air flow component 29moves inwardly towards the bases of fins 26 and 27.

Due to the diverging geometry of fins 26 and 27, air flow from thetangential component 29, as well as air flow from the axial component(not seen in FIG. 3), moves towards the fin tips to escape the regionbetween adjacent fins 26 and 27, and thus little air flow reaches thehottest part of fins 26 and 27 near core 41. This results in inefficientthermal dissipation. Consequently, a more powerful and noisier fan mustbe substituted, or the electronic component will not be sufficientlycooled to avoid performance degradation or catastrophic failure.

FIG. 4 is a side view of a section, taken between dashed line segments24 and 25 of FIG. 2, of a prior art radial fin heat sink 20 positionedupon an IC package 34. Fins 31 and 32 are on opposite sides of heat sink20. The lower surface of thermal plug 40 is in thermal contact with theupper surface of a heat-producing IC package 34. Heat, represented byarrows 35, is transferred from IC package 34 into thermal plug 40. Fromthermal plug 40, heat is transferred through sidewall 38 of cavity 23 tofin 31 (the heat sink core has been omitted to simplify thisillustration), and through sidewall 39 of cavity 23 to fin 32. Thehottest part of fins 31 and 32 is nearest the thermal plug 40.

A group 36 of air flow vectors is schematically shown to represent anaxial air flow component produced by an axial flow fan (not shown)downward between adjacent fins, including fin 31, of prior art radialfin heat sink 20. It will be seen that little if any air flow movesagainst the hottest part of fin 31 nearest thermal plug 40.

Likewise, another group 37 of air flow vectors represents an axial airflow component produced by the axial flow fan (not shown) downwardbetween adjacent fins, including fin 32. Again, little if any air flowmoves against the hottest part of fin 32 nearest thermal plug 40.

In addition, it is not readily apparent from FIGS. 3 and 4, but only aninsubstantial amount of air flow from the tangential component producedby a typical axial flow fan is captured by the prior art radial fin heatsink. This is illustrated further below regarding FIG. 18.

It should be apparent that what is needed is a heat sink structure thatsignificantly increases the amount of air impinging upon the hottestpart of the heat sink, and that significantly increases the volume andvelocity of air moving through the heat sink fins, includingsignificantly increasing the amount of the tangential component of anaxial flow fan that is captured by the heat sink.

FIG. 5 illustrates a perspective view of a curved fin heat sink 50, inaccordance with an embodiment of the inventive subject matter. Curvedfin heat sink 50 comprises a plurality of cooling fins 52 arranged abouta core 55. Fins 52 are formed of a material having high thermalconductivity such as a thermally conductive metal. In one embodiment,fins 52 are formed of aluminum; however, they could also be formed ofcopper or any other suitable thermally conductive metal or metal alloy.

Core 55 has a central axis 58. Core 55 can optionally have a centralcavity 54 for insertion of a thermal plug (not shown). Each fin 52 has abase and a tip. The base of each fin 52 is coupled to core 55substantially parallel to central axis 58. It will be seen from FIG. 5that the tips of fins 52 define the periphery of a face to face thecomponent (e.g. IC package 64, FIG. 7), and that the face comprisesinter-fin openings in the form of spaces between individual fins 52.Each fin 52 is curved in the same relative direction. As will be seenfrom the description below, the fins 52 of curved fin heat sink 50 areshaped to capture the tangential component of air from an axial flow fan(not shown in FIG. 5). Fins 52 are also shaped to direct a relativelylarge volume and relatively high velocity of air flow to contactsubstantially the entire surface of each fin 52, including the hottestportion of each fin 52 adjacent the core 55.

FIG. 6 illustrates a top view of the curved fin heat sink 50 shown inFIG. 5. An explanation will now be given as to how curved fin heat sink50 is shaped in order to maximize the number of cooling fins 52 for adesired “semi-rectangular” shape of curved fin heat sink 50 whilemaintaining a substantially uniform aspect ratio among all of coolingfins 52. “Semi-rectangular” is defined herein to mean a geometricalfigure having four straight or slightly curved (either concave orconvex) sides that meet at corners that are perpendicular, rounded,and/or otherwise different from perpendicular.

A semi-rectangular shape was chosen for one embodiment of curved finheat sink 50, because that shape most closely matched the footprint of ahigh performance IC package on which curved fin heat sink 50 wasmounted. A further constraint on the shape of curved fin heat sink 50,in this embodiment, was a “keep-out area” on the circuit board aroundthe IC package, due to the necessity of mounting other components in thekeep-out area and of minimizing the overall physical size of the circuitboard.

The semi-rectangular shape of curved fin heat sink 50 can be seen inFIG. 6, in that curved fin heat sink 50 comprises two slightlyconvex-curved sides of length 61 and two slightly convex-curved ends oflength 62. Each side meets a respective end at a rounded corner such ascorner 57.

Fins 52 are fabricated, in one embodiment, through an extrusion process.By using an extrusion process, heat sinks can be made at a significantsavings in manufacturing costs as compared with a process, for example,in which fins are machined from a heat sink core, or brazed or solderedonto a heat sink core. Using high volume manufacturing techniques,extrusions several feet long can be quickly formed and then cut intoindividual curved fin heat sinks, each having a plurality of curved finsand, optionally if desired, a central cavity to accommodate a thermalplug.

However, the extrusion process for curved fins is currently subject toseveral process constraints. One constraint is that for extrudingaluminum, for example, the aspect ratio of a curved fin 52, i.e. theratio of the length of a fin 52 to the average width of the gap betweentwo adjacent fins 52, cannot exceed about 10:1 to 12:1. Anotherconstraint is that the radius at the base of the fins cannot be lessthan about 1.0 to 1.2 millimeters.

Yet another constraint is to provide as many fins 52 as possible(subject to the above-mentioned radius constraint), with each fin 52 aslong as possible (subject to the above-mentioned aspect ratioconstraint), in order to provide as great a total heat dissipationsurface as possible. In the situation where the heat sink is being usedto cool an IC, the heat dissipation from the heat sink must be at leastsufficient to maintain a junction temperature within the IC at or belowa predetermined maximum value.

In view of the above-mentioned process constraints, the core 55 isshaped to substantially match the shape or footprint of curved fin heatsink 50, which in the embodiment shown in FIG. 6 is a semi-rectangularshape. Thus, core 55 comprises two slightly convex-curved sides oflength 71 and two slightly convex-curved ends of length 72. Each sidemeets a respective end at a rounded corner such as corner 77. As aresult, the aspect ratio of fins 52 can be maintained substantiallyuniform around the entire periphery of curved fin heat sink 50. Somevariation in aspect ratio of fins 52 around the periphery of curved finheat sink 50 is acceptable, so long as the maximum aspect ratio ofapproximately 10:1 to 12:1 is not exceeded for any fin 52. It will beunderstood that with advances in extrusion technology the upper end ofthe aspect ratio range can be expected to rise; however, the sameprinciples of the disclosure will nonetheless be applicable to heatssinks extruded with more advanced extrusion technology.

FIG. 7 illustrates a perspective view of an electronic assembly 60including a curved fin heat sink 50 positioned upon an IC package 64, inaccordance with an embodiment of the inventive subject matter. ICpackage 64 is shown mounted upon a circuit board 63, which can be ofsimilar or identical type to the prior art circuit board illustrated inFIG. 1; however, circuit board 63 can be of any type. The lower face ofcurved fin heat sink 50 is in thermal contact with IC package 64.

An axial flow fan 65 is shown schematically positioned over the upperface of curved fin heat sink 50. Fan 65 comprises a plurality of fanblades or impellers 66 that rotate, in the direction indicated by arrow68, about an axis 67 that is substantially perpendicular to the upperface of curved fin heat sink 50.

Because heat sink 50 is considerably less expensive to fabricate, andhas considerably less mass, than the prior art heat sink 2 illustratedin FIG. 1, electronic assembly 60 is more commercially desirable thanthe prior art electronic assembly 1 illustrated in FIG. 1

FIG. 8 illustrates a perspective view of a portion of an electronicassembly including an axial flow fan 70 atop a curved fin heat sink 50,in accordance with an embodiment of the inventive subject matter. Fan 70comprises a plurality of curved blades 74 disposed about an axis 69 thatis substantially perpendicular to the upper face of curved fin heat sink50. Blades 74 are attached to a hub 84 that is driven, in the directionof rotation indicated by arrow 75, by fan motor 73. A hold-downmechanism 76 is used to clamp fan 70 and curved fin heat sink 50 to theupper surface of a heat-producing IC (not shown) on a circuit board (notshown) underlying curved fin heat sink 50.

FIG. 9 illustrates a top view of the portion within dashed rectangle 56of FIG. 6, showing an air flow pattern within fins 81 and 82 of curvedfin heat sink 50, in accordance with an embodiment of the inventivesubject matter. In FIG. 9, a tangential air flow component 79 from anaxial flow fan (not shown) impinges upon fins 81 and 82. Each fin, suchas fin 81 or 82, is curved towards, or faces, counter to the directionof rotation 75 of fan blades 74 (FIG. 8).

Before discussing tangential air flow component 79, it should be firstnoted that the base regions of fins 81 and 82 are substantiallyperpendicular to core 55. From their bases, fins 81 and 82 curvesubstantially away from the perpendicular. However, fins 81 and 82diverge only slightly as they emanate from core 55. The radius 78 at thebase of fins 81 and 82 is only slightly smaller than the fin tipdistance 88 at the tips of fins 81 and 82. This geometry providessignificantly improved air flow between fins 81 and 82. It provides amore constricted path towards the tips of the fins, thus retaining moreof the air flow between the fins, where it can dissipate heat from thefins.

Tangential air flow component 79 impinges against the fins of curved finheat sink 50, such as fins 81 and 82. A relatively small portion 80 oftangential air flow component 79 moves outwardly towards the tips offins 81 and 82. A significantly larger portion 83 of tangential air flowcomponent 79 moves inwardly towards the bases of fins 81 and 82. Thus,significantly more air flow is directed towards the hottest part of heatsink, i.e. core 55 and particularly the base portions of fins 81 and 82near core 55. Because air flow is directed inwardly toward the core, insome embodiments a fan shroud, which would block air flow from exitingout the tips of the fins, may be dispensed with, thus offeringsignificant cost, mass, and reliability advantages.

FIG. 10 illustrates a side view of a section of the curved fin heat sink50 shown in FIG. 6, taken between dashed line segments 51 and 53. Fins91 and 92 are on opposite sides of curved fin heat sink 50. The lowersurface of thermal plug 90 is in thermal contact with the upper surfaceof a heat-producing IC package 94. Heat, represented by arrows 95, istransferred from IC package 94 into thermal plug 90. From thermal plug90, heat is transferred through sidewall 98 of cavity 54 to fin 91 (theheat sink core has been omitted to simplify this illustration), andthrough sidewall 99 of cavity 54 to fin 92. The hottest part of fins 91and 92 is nearest the thermal plug 90.

A group 96 of air flow vectors is schematically shown to represent anair flow component produced by an axial flow fan (not shown) downwardbetween adjacent fins, including fin 91, of curved fin heat sink 50(FIG. 6). Still referring to FIG. 10, it will be seen that substantiallymore air flow moves against the hottest part of fin 91 nearest thermalplug 90 than in the prior art radial fin heat sink 20, as was discussedearlier regarding FIG. 4. The increase in air flow is produced by thecurved fin geometry, which not only curves the fins to capture both thenormal and tangential components of the air flow from the axial flowfan, but which also has an inter-fin space of near uniform width toallow air to move down between the fins at a higher volume and higherspeed than if the fins widened towards their tips, as in the prior artheat sink 20 shown in FIG. 2.

Still referring to FIG. 10, another group 97 of air flow vectorsrepresents an air flow component produced by the axial flow fan (notshown) downward between adjacent fins, including fin 92. Again,substantially more air flow moves against the hottest part of fin 92nearest thermal plug 90.

In addition, although it is not readily apparent from FIGS. 9 and 10, asubstantial amount of air flow from the tangential component produced bya typical axial flow fan is captured by the fins of curved fin heat sink50 (FIG. 6). This again is achieved by the curved fin geometry thatcurves the fins towards the tangential component of air flow.

Thus, the curved fin heat sink 50 (FIG. 6) significantly increases theamount of air impinging upon the hottest part of the curved fin heatsink 50, and it significantly increases the volume and velocity of airmoving through the curved fin heat sink 50, including significantlyincreasing the amount of the tangential component of an axial flow fanthat is captured by the curved fin heat sink 50.

In addition, an axial flow fan used in conjunction with curved fin heatsink 50 can have a relatively low rotational speed, thus keeping fannoise to a minimum, while nonetheless producing sufficient air flow todissipate heat from a heat-generating component in an electronicassembly.

FIG. 11 illustrates a perspective view of a bent fin heat sink 100, inaccordance with an embodiment of the inventive subject matter. Bent finheat sink 100 comprises a plurality of cooling fins 102 arranged about acore 105. Fins 102 are formed of a thermally conductive metal. In oneembodiment, fins 102 are formed of aluminum; however, they could also beformed of copper or any other suitable thermally conductive metal ormetal alloy.

Core 105 has a central axis 101. Core 105 can optionally have a centralcavity 106 for insertion of a thermal plug (not shown). Each fin 102 hasa base and a tip. The base of each fin 102 is coupled to core 105substantially parallel to central axis 101.

Each fin 102 comprises a vertical portion 107 and an angled portion 108.The angled portion 108 of each fin 102 is bent in the same relativedirection. As will be seen from the description below, the fins 102 ofbent fin heat sink 100 are shaped to capture the tangential component ofair from an axial flow fan (not shown in FIG. 11). They are also shapedto direct a relatively large and relatively high velocity air flow tocontact substantially the entire surface of each fin 102, including thehottest portion of each fin 102 adjacent the core 105.

According to one embodiment of a bent fin heat sink 100, after forming(e.g. by extrusion) a plurality of straight unbent fins emanatingradially from core 105, the upper portion of the heat sink 100 iscounterbored to produce a counterbore 104, in which part of the base ofeach fin 102 is sheared from core 105 in the vicinity only of angledportion 108. This allows angled portion 108 of each fin 102 to be bentin a subsequent operation.

In one embodiment, the angle that the angled portion 108 of each finmakes with the vertical portion 107 is approximately 150 degrees. Inother embodiments, different angles could be used, depending upon theair flow characteristics of the particular axial flow fan being used inconjunction with the bent fin heat sink.

Instead of counterboring the upper portion of heat sink 100, a hole sawor other tool could be utilized to make a groove in the upper portion ofheat sink 100 of sufficient depth to enable the angled portion 108 ofeach fin 102 to be bent.

It will be noted that for certain fins in the “corner” regions of bentfin heat sink 100, their upper tips 109 are slightly clipped to fit intoa desired “semi-rectangular” (as earlier defined) footprint. However, inother embodiments, such clipping could be omitted.

FIG. 12 illustrates a top view of a bent fin heat sink 100, inaccordance with an embodiment of the inventive subject matter. Bent finheat sink 100 is shaped in order to maximize the number of cooling fins102 for a desired “semi-rectangular” shape of curved fin heat sink 100.

The semi-rectangular shape of curved fin heat sink 100 can be seen inFIG. 12, in that curved fin heat sink 100 comprises two substantiallystraight sides of length 111 and two substantially straight ends oflength 112. Each side meets a respective end at a rounded corner such ascorner 114.

Fins 102 are fabricated, in one embodiment, through an extrusionprocess. The extrusion process for bent fins is currently subject tobasically the same process constraints as for the curved fin heat sinkdescribed in FIG. 6, except that the aspect ratio of the fins 102 can beslightly greater than for curved fins, ranging up to approximately 14:1to 16:1.

In view of the fact that the fabrication of the angled portions 108 ofthe fins 102 of bent fin heat sink 100 requires counterboring acounterbore 104, the shape of core 105 is maintained generally circularin the embodiment shown in FIG. 12. However, in another embodiment, theshape of core 105 could be semi-rectangular, as in the embodiment shownin FIG. 6.

The trimmed upper tips 109 of certain fins 102 near the corners of heatsink 100 can be seen in FIG. 12.

FIG. 13 illustrates a perspective view of an electronic assembly 120including a bent fin heat sink 100 positioned upon an IC 124 package, inaccordance with an embodiment of the inventive subject matter.

IC package 124 is shown mounted upon a circuit board 122, which can beof similar or identical type to the prior art circuit board illustratedin FIG. 1; however, circuit board 122 can be of any type.

An axial flow fan 125 is shown schematically positioned over bent finheat sink 100. Fan 125 comprises a plurality of fan blades or impellers126 that rotate, in the direction indicated by arrow 128, about an axis127 that is substantially perpendicular to the upper face of bent finheat sink 100. Bent fin heat sink 100, in this embodiment, comprises athermal plug 123. Thermal plug 123 can be formed of any suitablethermally conductive material. In one embodiment, thermal plug 123 ismade of copper; however, aluminum or a copper or aluminum alloy couldalso be used.

FIG. 14 illustrates a schematic view of a fan 135, including itstangential air flow component 130 and its normal air flow component 132,and a side view of a bent fin heat sink 100 as positioned upon asectioned IC package 150 on a substrate 160, in accordance with anembodiment of the inventive subject matter.

Fan 135 can be similar or identical to fan 70 shown in FIG. 8. Fan 135is an axial flow fan having a plurality of fan blades 136, rotating in adirection indicated by arrow 138, and disposed about an axis of rotation137.

Fan 135, when rotating about axis 137, produces an air flow that can beanalyzed as having two different components. A tangential component 130comprises a plurality of angular vectors 131 generally increasingtowards the fan blade periphery. An axial component 132 comprises aplurality of downward vectors 133, again generally increasing towardsthe fan blade periphery.

Because the fins 102 of bent fin heat sink 100 are angled towards, orface, the tangential component 130, a relatively greater air flow,represented by arrows 140, is captured and flows downward between fins102, exiting in the direction of arrows 142 beneath bent fin heat sink100.

Thermal plug 123 of bent fin heat sink 100 is in thermal contact with anIC package 150. IC package 150, illustrated in cross-section, includes adie 154 mounted on a package substrate 152 and covered with a lid orintegrated heat spreader (IHS) 158. A thermal grease or phase changematerial 156 can be used between die 154 and IHS 158. Likewise, athermal grease or phase change material (not shown) can be used, ifdesired, between IHS 158 and thermal plug 123. Some of the relativedimensions of the structures shown in FIG. 14 are exaggerated ordiminished, and they are not drawn to scale. For example, in a differentembodiment the thermal plug 123 could be as wide as IHS 150, with bentfin heat sink 100 accordingly widened to accommodate an IHS 150 of suchwidth.

FIG. 15 illustrates a perspective view of a curved-bent fin heat sink200, in accordance with an embodiment of the inventive subject matter.Curved-bent fin heat sink 200 comprises a plurality of cooling fins 202arranged about a core 205. Fins 202 are formed of a thermally conductivemetal. In one embodiment, fins 202 are formed of aluminum; however, theycould also be formed of copper or any other suitable thermallyconductive metal or metal alloy.

Core 205 has a central axis 201. Core 205 can optionally have a centralcavity 206 for insertion of a thermal plug (not shown). Each fin 202 hasa base and a tip. The base of each fin 202 is coupled to core 205substantially parallel to central axis 201. Each fin 202 is curvedbetween its base and its tip, and the curve of each fin 202 is towardsthe same relative direction. In the embodiment shown in FIG. 15, eachfin 202 is curved towards, or faces, a counterclockwise direction,opposite to the direction of rotation of an axial flow fan to be used inconjunction with heat sink 200.

Each fin 202 comprises a vertical portion 207 and an angled portion 208.The angled portion 208 of each fin 202 is bent in the same relativedirection. As will be seen from the description below, the fins 202 ofcurved-bent fin heat sink 200 are shaped to capture the tangentialcomponent of air from an axial flow fan (not shown in FIG. 15 but shownin FIG. 17). They are also shaped to direct a relatively large andrelatively high velocity air flow to contact substantially the entiresurface of each fin 202, including the hottest portion of each fin 202adjacent to the core 205.

According to one embodiment of a curved-bent fin heat sink 200, afterforming a plurality of curved unbent fins emanating substantiallyradially from core 205, for example using an extrusion process, theupper portion of the heat sink 200 is counterbored to produce acounterbore 204 in which part of the base (i.e. inner portion) of eachfin 202 is sheared from core 205 in the vicinity only of angled portion208. This allows angled portion 208 of each fin 202 to be bent in asubsequent operation.

In one embodiment, the angle that the angled portion 208 of each finmakes with the vertical portion 207 is approximately 150 degrees. Inother embodiments, different angles could be used, depending upon theair flow characteristics of the particular axial flow fan being used inconjunction with the bent fin heat sink.

FIG. 16 illustrates a top view of a curved-bent fin heat sink 200, inaccordance with an embodiment of the inventive subject matter.Curved-bent fin heat sink 200 is shaped in order to maximize the numberof cooling fins 202 for a desired “semi-rectangular” shape ofcurved-bent fin heat sink 200.

The semi-rectangular shape of curved-bent fin heat sink 200 can be seenin FIG. 16, in that curved-bent fin heat sink 200 comprises two slightlyconvex-curved sides of length 211 and two slightly convex-curved ends oflength 212. Each side meets a respective end at a rounded corner such ascorner 214.

Fins 202 are fabricated, in one embodiment, through an extrusion processfollowed by a counterboring process and then a bending process. Theextrusion process for curved-bent fins is currently subject to basicallythe same process constraints as for the curved fin heat sink describedin FIG. 6. For this reason, the core 205 is shaped to substantiallymatch the shape or footprint of curved-bent fin heat sink 200, which inthe embodiment shown in FIG. 16 is a semi-rectangular shape.

Thus, core 205 comprises two slightly convex-curved sides of length 231and two slightly convex-curved ends of length 232. Each side meets arespective end at a rounded corner such as corner 234. As a result, theaspect ratio of the fins can be maintained substantially uniform aroundthe entire periphery of curved-bent fin heat sink 200. Some variation inaspect ratio of the fins around the periphery of curved-bent fin heatsink 200 is acceptable, so long as the maximum aspect ratio ofapproximately 10:1 to 12:1 is not exceeded for any fin.

FIG. 17 illustrates a perspective view of an electronic assembly 220including a curved-bent fin heat sink 200 positioned upon an IC package224, in accordance with an embodiment of the inventive subject matter.

IC package 224 is shown mounted upon a circuit board 222, which can beof similar or identical type to the prior art circuit board illustratedin FIG. 1; however, circuit board 222 can be of any type.

An axial flow fan 225 is shown schematically positioned over curved-bentfin heat sink 200. Fan 225 comprises a plurality of fan blades orimpellers 226 that rotate, in the direction indicated by arrow 228,about an axis 227 that is substantially perpendicular to the upper faceof curved-bent fin heat sink 200. Curved-bent fin heat sink 200, in thisembodiment, comprises a thermal plug 223.

FIG. 18 illustrates an air flow pattern 250 for a prior art radial finheat sink. Straight, vertical, radially-attached fins 251 each receivean air flow vector 255 from an axial flow fan (not shown) above the heatsink. As mentioned earlier, an axial flow fan produces an air flowhaving both an axial component directed substantially perpendicular tothe upper face of the heat sink, and a tangential component in thedirection of rotation of the fan blades.

In FIG. 18, substantially all of the tangential component 256 of airflow vector 255 is deflected away from the opening between adjacent fins251. The predominant component of air flow into the space betweenadjacent fins 251 is the axial component 257. However, a portion ofaxial component 257 is also deflected away and does not go betweenadjacent fins 251, due to the vertical geometry of the fins. For thisfin geometry, there is increased air pressure between the fins,resulting in reduced mass flow and decreased heat dissipationperformance.

FIG. 19 illustrates an air flow pattern 260 for a bent fin heat sink, inaccordance with an embodiment of the inventive subject matter. Bent,radially-attached fins 261 each receive an air flow vector 265 from anaxial flow fan (not shown) above the heat sink.

In FIG. 19, substantially all of the tangential component of air flowvector 265 is captured by the angled portions 269 of fins 261 and goesinto the space between adjacent fins 261, including vertical portions268, which are the hottest portions of fins 261. Only a small component266 of the tangential component is deflected away. In addition, littleof the axial component 267 is deflected away, as occurs with the heatsink fin geometry of the prior art straight, radial fin heat sinkillustrated in FIG. 18, and most of axial component 267 goes betweenadjacent fins 261.

FIG. 20 illustrates an air flow pattern 270 for a curved-bent fin heatsink, in accordance with an embodiment of the inventive subject matter.Curved-bent, radially-attached fins 271 each receive an air flow vector275 from an axial flow fan (not shown) above the heat sink.

In FIG. 20, substantially all of the tangential component of air flowvector 275 is captured by the angled portions 279 of fins 271 and goesinto the space between adjacent fins 271, including vertical portions278, which are the hottest portions of fins 271. Only a small component276 of the tangential component is deflected away. In addition, littleof the axial component 277 is deflected away, as occurs with the heatsink fin geometry of the prior art straight, radial fin heat sinkillustrated in FIG. 18, and most of axial component 277 goes betweenadjacent fins 271.

In addition, the curvature of fins 271 assists in directing the air flowinward towards the heat sink core (not shown, but in this view it wouldbe behind fins 271). Because substantial air flow from the fan (notshown) is captured by the curved-bent heat sink, and because thecaptured air flow is directed inward towards the heat sink core and thehottest part of fins 271 (next to the core), the curved-bent heat sinkis capable of dissipating a significant amount of heat from aheat-producing electronic component with which it is used.

In summary, for the fin geometries of the bent fin heat sink and thecurved-bent fin heat sink, there is decreased air pressure between thefins, resulting in increased mass flow and increased heat dissipationperformance.

FIG. 21 illustrates a flow diagram of a method of fabricating a heatsink, in accordance with an embodiment of the inventive subject matter.The method begins at 300.

In 302, a billet of thermally conductive metal, such as aluminum orcopper, is obtained.

In 304, a plurality of fins are formed from the billet, for example byan extrusion or micro-forging process. The fins extend outwardly from acore in an asymmetric pattern (in the case of curved fins). The core hasa central axis, and each fin has a base that is coupled to the coresubstantially parallel to the central axis. If desired, a central cavitycan be formed in the core. The central cavity can be formed in anysuitable manner, for example as part of the extrusion operation.

In 306, if the fins are to be bent, the process goes to 308; otherwise,it goes to 312.

In 308, the portions of the fins to be bent are separated from the core,for example by forming a cavity (e.g. by counterboring) or channel (e.g.by machining or sawing) into the core a predetermined distance along thecentral axis, from the top of the heat sink.

In 310, a portion of each fin is bent in substantially the same relativedirection. In one embodiment, the upper portion of each fin is bent downapproximately 30 degrees from vertical, so that the angled portion ofthe fin forms an angle of approximately 150 degrees with the verticalportion of the fin.

In 312, which is optional depending upon whether a central cavity wasformed in 304, a thermal plug is inserted into the central cavity toprovide increased thermal dissipation from the IC through the heat sinkcore to the heat sink fins. The process ends at 314.

FIG. 22 illustrates a flow diagram of a method of fabricating anelectronic assembly, in accordance with an embodiment of the inventivesubject matter. The process begins at 400.

In 402, an electronic component is mounted on a circuit board.

In 404, an axial flow fan is provided. The axial flow fan is capable ofmoving air having a component normal to the electronic component and acomponent tangential to the electronic component.

In 406, a heat sink is mounted between the electronic component and theaxial flow fan. The heat sink includes a number of cooling fins that arearranged about a core having a central axis. Each cooling fin has a basecoupled to the core substantially parallel to the central axis. Thecooling fins are shaped to capture both components of air, i.e. theaxial component and the tangential component. A first face of the heatsink is in thermal contact with the electronic component and has asemi-rectangular periphery. A second face of the heat sink faces the fanand has a semi-rectangular periphery. The second face is substantiallyopposite the first face. The core is shaped to maximize the number ofcooling fins while maintaining a substantially uniform aspect ration inthe cooling fins. The method ends at 408.

The operations described above with respect to FIGS. 21 and 22 could beperformed in a different order from those described herein. Also,although the flow diagrams of FIGS. 21 and 22 are shown as having abeginning and an end, they can be performed continuously.

FIG. 23 is a block diagram of an electronic system 501 incorporating atleast one electronic assembly 502 with at least one high capacity heatsink, in accordance with an embodiment of the inventive subject matter.Electronic system 501 is merely one example of an electronic system inwhich embodiments of the inventive subject matter can be used. In thisexample, electronic system 501 comprises a data processing system thatincludes a system bus 504 to couple the various components of thesystem. System bus 504 provides communications links among the variouscomponents of the electronic system 501 and can be implemented as asingle bus, as a combination of busses, or in any other suitable manner.

Electronic assembly 502 is coupled to system bus 504. Electronicassembly 502 can include any circuit or combination of circuits. In oneembodiment, electronic assembly 502 includes a processor 506 which canbe of any type. As used herein, “processor” means any type ofcomputational circuit, such as but not limited to a microprocessor, amicrocontroller, a complex instruction set computing (CISC)microprocessor, a reduced instruction set computing (RISC)microprocessor, a very long instruction word (VLIW) microprocessor, agraphics processor, a digital signal processor (DSP), or any other typeof processor or processing circuit.

Other types of circuits that can be included in electronic assembly 502are a chip set 507 and a communications circuit 508. Chip set 507 andcommunications circuit 508 are functionally coupled to processor 506,and they can be configured to perform any of a wide number of processingand/or communications operations. Other possible types of circuits (notshown) that could be included within electronic assembly 502 include adigital switching circuit, a radio frequency (RF) circuit, a memorycircuit, a custom circuit, an application-specific integrated circuit(ASIC), an amplifier, or the like.

Electronic system 501 can also include an external memory 512, which inturn can include one or more memory elements suitable to the particularapplication, such as a main memory 514 in the form of random accessmemory (RAM), one or more hard drives 516, and/or one or more drivesthat handle removable media 518 such as floppy diskettes, compact disks(CDs), digital video disks (DVDs), and the like.

Electronic system 501 can also include a display device 509, one or morespeakers 510, and a keyboard and/or controller 520, which can include amouse, trackball, game controller, voice-recognition device, or anyother device that permits a system user to input information into andreceive information from the electronic system 501.

FIGS. 1–20 and 23 are merely representational and are not drawn toscale. Certain proportions thereof may be exaggerated, while others maybe minimized. FIGS. 5–17, 19, 20, and 23 are intended to illustratevarious implementations of the inventive subject matter that can beunderstood and appropriately carried out by those of ordinary skill inthe art.

The inventive subject matter provides for a heat sink and an electronicassembly that minimize thermal dissipation problems associated with highpower delivery, and to methods of manufacture thereof. An electronicsystem and/or data processing system that incorporates one or moreelectronic assemblies that utilize the inventive subject matter canhandle the relatively high power densities associated with highperformance integrated circuits, and such systems are therefore morecommercially attractive.

By substantially increasing the thermal dissipation from highperformance electronic assemblies, such electronic equipment can beoperated at increased clock frequencies. Alternatively, such equipmentcan be operated at reduced clock frequencies but with lower operatingtemperatures for increased reliability.

As shown herein, the inventive subject matter can be implemented in anumber of different embodiments, including a heat sink, an electronicassembly, an electronic system, and various methods, including a methodof fabricating a heat sink, and a method of fabricating an electronicassembly. Other embodiments will be readily apparent to those ofordinary skill in the art. The elements, materials, geometries,dimensions, and sequence of operations can all be varied to suitparticular packaging and heat-dissipation requirements.

While certain operations have been described herein relative to “upper”and “lower” surfaces, it will be understood that these descriptors arerelative, and that they would be reversed if the relevant structure(s)were inverted. Therefore, these terms are not intended to be limiting.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for a specific embodiment shown. This application coversany adaptations or variations of the inventive subject matter.Therefore, it is manifestly intended that embodiments of this subjectmatter be limited only by the claims and the equivalents thereof.

1. A heat sink for use with an axial flow fan comprising: a core havinga central axis; and a plurality of cooling fins arranged about the core,each fin having a base and a tip, wherein the bases are coupled to thecore substantially parallel to the central axis, wherein the fins areshaped to capture a tangential component of air from the fan, whereinthe fins are curved towards the tangential component, and wherein anupper portion of each of the fins is bent towards the tangentialcomponent.
 2. The heat sink recited in claim 1, wherein the fins areformed of aluminum, and wherein the radius at the base of the fins is inthe range of 1.0 to 1.2 millimeters.
 3. The heat sink recited in claim 1and further comprising: a first face having a semi-rectangular peripherythat is defined by the fin tips, and which is to thermally contact aheat-generating electrical component.
 4. The heat sink recited in claim3 and further comprising: a second face, substantially opposite thefirst face, and having a semi-rectangular periphery that is defined bythe fin tips.
 5. The heat sink recited in claim 1 wherein the corecomprises a central cavity to receive a thermal plug formed of amaterial having a high thermal conductivity.
 6. A heat sink for use withan axial flow fan comprising: a core having a central axis; and aplurality of cooling fins arranged about the core, each fin having abase and a tip, wherein the bases are coupled to the core substantiallyparallel to the central axis, wherein the fins are shaped to capture atangential component of air from the fan, wherein the fins are curvedtowards the tangential component, wherein an upper portion of each ofthe fins is bent towards the tangential component, and wherein the coreis shaped to maximize the number of fins while maintaining asubstantially uniform aspect ratio in the fins.
 7. The heat sink recitedin claim 6, wherein the fins are formed of aluminum, and wherein theaspect ratio of the fins is in the range of 10:1 to 12:1 or in the rangeof 14:1 to 16:1.
 8. The heat sink recited in claim 6, wherein the heatsink is to dissipate heat from an integrated circuit (IC), wherein thefins are formed of material having a high thermal conductivity, andwherein the aspect ratio of the fins is sufficient to maintain ajunction temperature within the IC at or below a predetermined maximumvalue.
 9. The heat sink recited in claim 6, wherein the fins are formedof aluminum, and wherein the radius at the base of the fins is in therange of 1.0 to 1.2 millimeters.
 10. The heat sink recited in claim 6and further comprising: a first face having a semi-rectangular peripherythat is defined by the fin tips, and which is to thermally contact aheat-generating electrical component.
 11. The heat sink recited in claim10 and further comprising: a second face, substantially opposite thefirst face, and having a semi-rectangular periphery that is defined bythe fin tips.
 12. The heat sink recited in claim 6 wherein the corecomprises a central cavity to receive a thermal plug formed of amaterial having a high thermal conductivity.
 13. An electronic assemblycomprising: a substrate; an electronic component mounted on a surface ofthe substrate; an axial flow fan to move air towards the substrate, theair having an axial component and a tangential component; and a heatsink including a first face in thermal contact with the electroniccomponent; a second face facing the fan; a core having a central axis;and a plurality of cooling fins arranged about the core, each fin havinga base and a tip, wherein the bases are coupled to the coresubstantially parallel to the central axis, wherein the fins are shapedto capture both components of air, wherein the fins are curved towardsthe tangential component, and wherein an upper portion of each of thefins is bent towards the tangential component.
 14. The electronicassembly recited in claim 13, wherein the core is shaped to maximize thenumber of fins while maintaining a substantially uniform aspect ratio inthe fins.
 15. The electronic assembly recited in claim 13, wherein theelectronic component comprises an integrated circuit (IC).
 16. Theelectronic assembly recited in claim 15, wherein the fins are formed ofmaterial having a high thermal conductivity, and wherein the aspectratio of the fins is sufficient to maintain a junction temperaturewithin the IC at or below a predetermined maximum value.
 17. A method ofmaking an electronic assembly, the method comprising: mounting anelectronic component on a circuit board; providing an axial flow fan,the fan capable of moving air having a component normal to theelectronic component and a component tangential to the electroniccomponent; and mounting a heat sink between the electronic component andthe fan, the heat sink comprising a plurality of cooling fins arrangedabout a core having a central axis, each fin having a base coupled tothe core substantially parallel to the central axis, wherein the coolingfins are shaped to capture both components of air, wherein the fins arecurved towards the tangential component, and wherein an upper portion ofeach of the fins is bent towards the tangential component.
 18. Themethod recited in claim 17, wherein the electronic component is from thegroup consisting of a processor, a chipset integrated circuit (IC), adigital switching circuit, a radio frequency (RF) circuit, a memorycircuit, a custom circuit, an application specific IC (ASIC), and anamplifier.
 19. The method recited in claim 17, wherein the core isshaped to maximize the number of fins while maintaining a substantiallyuniform aspect ratio in the fins.
 20. The method recited in claim 17,wherein each fin has a tip, wherein a first face of the heat sink is inthermal contact with the electronic component and has a semi-rectangularperiphery that is defined by the fin tips, and wherein a second face ofthe heat sink, substantially opposite the first face, faces the fan andhas a semi-rectangular periphery that is defined by the fin tips.